Abstract

We present a theoretical scheme for a semiquantitative analysis of electronic structures of magnetic transition metal dimer complexes within spin density functionaltheory(DFT). Based on the spin polarization perturbational orbital theory [D.-K. Seo, J. Chem. Phys.125, 154105 (2006)], explicit spin-dependent expressions of the spin orbital energies and coefficients are derived, which allows to understand how spin orbitals form and change their energies and shapes when two magnetic sites are coupled either ferromagnetically or antiferromagnetically. Upon employment of the concept of magnetic orbitals in the active-electron approximation, a general mathematical formula is obtained for the magnetic coupling constant from the analytical expression for the electronic energy difference between low-spin broken-symmetry and high-spin states. The origin of the potential exchange and kinetic exchange terms based on the one-electron picture is also elucidated. In addition, we provide a general account of the DFT analysis of the magnetic exchange interactions in compounds for which the active-electron approximation is not appropriate.

Received 02 July 2007Accepted 21 August 2007Published online 09 November 2007

Acknowledgments:

This work was supported by the National Science Foundation through the author’s CAREER Award (DMR, Contract No. 0239837) and also partly by his Camille Dreyfus Teacher-Scholar Award from the Camille and Henry Dreyfus Foundation. The author would like to thank Dr. Stéphane Jobic for his hospitality at Jean Rouxel Institute of Materials in Nantes where the manuscript was written during the author’s stay.